Articulated vehicle

ABSTRACT

An articulated wheeled vehicle is disclosed herein having a front and a rear body portion pivotally joined together by a central axle rotatably mounted on opposing projections carried on the body portions. Axles are rotatably carried on each of the front and rear body portions so that a six-wheeled, three-axle vehicle is produced. Each axle comprises a pair of coextensive segments mounted in suitable bearings and each segment is separately powered via a drive train and transmission by a power plant so that directional control and speed of the vehicle can be attained since the axle segments may be rotated individually at different speeds and directions.

United States Patent 1151 3,659,666 Forsyth et al. 1 May 2, 1972 s41ARTICULATED VEHICLE 3,204,713 9/1965 Shanahan =1 al 180/648 x 1121 PM;RM W. both 3:321:23; 11323 fiiil'r'r'i'jjiiififfifi .i:::.'.f..fii7

[22] Filed: Oct. 2, 1969 [21] Appl. No.: 870,438

[52] US. Cl. ..180/6.2, 115/1 R, 180/23 [51] Int. Cl. .3621] 11/02 [58]Field of Search ..180/6.2, 6.48, 22, 23, 24, 180/51, 52; 280/52; 115/1 R[56] References Cited UNITED STATES PATENTS 1,829,808 11/1931 Opolo..l80/6.2

3,129,780 4/1964 Uyehara 3,161,172 12/1964 Kassbohrer...

3,183,991 5/1965 Gamaunt 3,198,551 8/1965 Garner ..180/6.48 X

of 1517 North 3rd Avenue, San Bernardino, Calif. 91786 PrimaryExaminer-Benjamin Hersh Assistant Examiner-Leslie .l. PapernerAttorney-Roger A. Man's [5 7] ABSTRACT An articulated wheeled vehicle isdisclosed herein having a front and a rear body portion pivotally joinedtogether by a central axle rotatably mounted on opposing projectionscarried on the body portions. Axles are rotatably carried on each of thefront and rear body portions so that a six-wheeled, three-axle vehicleis produced. Each axle comprises a pair of coextensive segments mountedin suitable bearings and each segment is separately powered via a drivetrain and transmission by a power plant so that directional control andspeed of the vehicle can be attained since the axle segments may berotated individually at different speeds and directions.

7 Claims, 9 Drawlng Figures PATENTEUMLAY 2:922 3.669666 SHEET 2 BF 3INVENTORS JOHM P. FO/ZSVTH BROBEQ w. FZES'YTH ARTICULATED VEHICLEBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to articulated wheeled vehicles and, more particularly, to novelvehicles having pivotally mounted body portions and segmented axlesfully driven by a common power unit and operable to independentlycontrol vehicular direction and velocity.

2. Description of the Prior Art In the broad field of articulatedvehicles, conventional vehicles generally comprise two or more bodyelements with provision made for semi-independent motion of the elementswith respect to each other. The prior art is relatively extensive. Theart ranges from the very common truck-tractor and semitrailercombinations to rather complex, prototype military vehicles in whichprovision is made for semi-independent motion of the body elements inpitch, roll, and yaw.

Specifically related to this broad field are articulated vehicles inwhich the body elements of the vehicle are arranged so as to permitrotational displacements in a longitudinal, vertical plane as the bodyelements pivot about a lateral pitch axis. The most common example ofthis configuration is the prime mover and trailer joined by a ball-typehitch. Also, there may be vehicles designed in which relative motion inpitch is provided between body elements which are joined together in amore or less permanent manner.

The fundamental disadvantage,'common to all prior art insemi-permanently joined, articulated or hinged-frame vehicles is thatthe means employed to provide for semi-independent motion of the vehicleelements are costly, complex mechanisms, incorporating manyclose-fitting, precision parts, partially or completely exposed to theelements and the entry of foreign matter and, thus, prone to malfunctionand failure, and requiring constant maintenance.

This disadvantage is even more pronounced in those vehicles in whicharticulation or hinging of the vehicle elements is found in conjunctionwith an all-wheel drive system with power being transmitted from oneelement to the other by mechanical means routed through the articulationjoint. In addition to the joint itself, this generally involves the useofdrive shafts incorporating sliding sections in telescopingrelationship to accommodate changes in length from the centers ofconstant-velocity, universal joints. Such components are needed toassure constant rotational speed of the shafts on both sides of theuniversal joints through the whole 360 of rotation. As may be readilyappreciated, being exposed as they generally are, such drives requirecomplicated lubrication systems and a number of specially constructeddust and lubrication seals for the shafts and universals.

The problem is further compounded and the designs usually infinitelymore complex in such vehicles when they are configured to enableamphibious operation. Added to the normally difficult task of sealingthe body elements of the vehicle at the axles, is the problem of sealingaround the attachments and fittings of the articulation joint or hinge,and sealing around the drive shafts transmitting power between vehicleelements.

SUMMARY OF THE INVENTION Accordingly, the problems and difficultiesencountered with conventional articulated vehicles are obviated by thepresent invention which provides a wheeled vehicle constructed with apair of body portions joined at a central axle by mated projectionscarried on and integrally formed with the body portions. Means areprovided for rotatably securing the mated projections to the centralaxle so that, with the axle acting as a hinge pin, the body portions maybe rotatably displaced with respect to each other. Therefore, thevehicle is provided with the capability of following or conformingduring travel to irregularities in the terrain. A front and rear axleare rotatably carried on the pair of body portions respectively, so thata six-wheel, three-axled vehicle is produced. Each axle comprises a pairof coextensive linear segments and'each seg mentis rotatably driven by acommon power plant via a suitable drive train including a dual outputtransmission. Thereby, the axle segments may be independently driven interms of rotational direction and velocity so that a steerable vehicleis produced.

A major feature of the invention resides in the hinged construction andassembly of the vehicle body portions so as to provide semi-independent,rotational displacement of the body portions in a longitudinal, verticalplane as the portions pivot about a lateral pitch axis.

Therefore, it is among the primary objects of the present invention toprovide a ground vehicle with the capability of conforming toirregularities in terrain by permitting displacement, relative to eachother, of portions of the vehicles body and attached running gear.Conformance to terrain irregularities in this manner will enablemaintenance of full ground contact of all wheels at all times,permitting the development of maximum tractive effort, enabling thegeneration of maximum braking effect in emergencies, and resulting in anexceptionally stable vehicle.

Another object of this invention is to provide for the dirninishment anddamping .of the shocks incident to traveling over irregular terrainthrough close conformance of the vehicle's body and attached runninggear to the profile of the terrain, and by a progressively greaterconstraint of displacement of the vehicles body segments when verticallyaccelerated as obstacles are struck by the vehicless running gear.

Still another object of the invention is to provide a novel means ofenabling displacement, relative to each other, of the vehicle's bodyportions and attached running ear which is mechanically simple and,further, assuring that maximum use is made of standard vehicle parts andstructuresso that these vehicle parts and structures perform multiplefunctions, thereby reducing the total number of parts required pervehicle, keeping the total weight of the vehicle to a minimum andkeeping cost to a minimum.

A further object of this invention is to provide a means of hinging thebody portions of an all-wheel drive, ground vehicle in which meansmaximum compatibility is achieved with the requirements entailed'inmaking the vehicle waterworthy (for example, assuring buoyancy with awater-tight body) by virtue of keeping to an absolute minimum the numberof seals incorporated in the body portions for power-transmission means,axle shafts, and components of the hinging means.

Yet another object of the present invention is to provide a novelarticulated vehicle having segmented axle shafts whereby each segmentmay be individually controlled to effect selective steering andvelocity.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the present inventionwhich are believed to be novel are set forth with particularity in theappended claims. The present invention, both as to its organization andmanner of operation, together with further objects and advantagesthereof, may best be understood by reference to the followingdescription, taken in connection with the accompanying drawings, inwhich:

FIG. 1 is a side elevational view of the novel articulated vehicle ofthe present invention illustrated on level terrain;

FIGS. 2 and 3 are views similar to FIG. 1 showing the vehicle on unevenor irregular terrain;

FIG. 4 is an enlarged elevational view, partly in section, of thevehicle as taken in the direction of arrows 4-4 of FIG. 6;

FIG. 5 is a perspective fragmentary view of the central axle pivotallyjoining the front and rear portions of the vehicle;

FIG. 6 is a top plan view of the vehicle having a portion broken away toexpose underlying components;

FIG. 7 is a front elevational view, partly in section, showing thevehicle drive train;

FIG. 8 is a cross-sectional view of the central axle region as taken inthe direction of arrows 8-8 of FIG. 7; and

FIG. 9 is a transverse cross-sectional view of the axle drive trainshown in FIG. 4 as taken in the direction of arrows 9-9 thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1, 2, and 3,the articulated vehicle of the present invention is indicated in thegeneral direction of arrow 10 which includes a vehicle body comprising afront or forward portion 11 and a rear portion 12. The front portionincludes a set of wheels 13 while the rear portion 12 is rollablysupported on the terrain 14 via a set of wheels 15. Disposed between thefront and rear sets of wheels, there is provided a central set of wheels16 providing additional rolling support for the vehicle body.Preferably, the front portion 11 may be suitably occupied by the driverand includes the necessary controls 'for operating the vehicle. The rearportion 12 is employed for mounting a power plane 17 and may includeseats intended to be occupied by passengers, although the front portionmay readily accommodate passengers as well as the driver. As shown inthe figures, the front and rear portions are arranged in end-to-endrelationship having their adjacent and opposing ends supported by thecentral wheel set 16. Preferably, the opposing ends of the body portionare angularly displaced with respect to each other so as to permitrelative movement therebetween as indicated in FIGS. 2 and 3 when thevehicle is traversing irregular terrain. It is to be particularly notedthat all three wheel sets are rollably engaged with the surface of theterrain whether or not that surface is smooth or irregular. As aconsequence, increased traction and vehicle stability is effected.

Referring now to FIG. 4, it can be seen that the opposing end surfaces20 and 21 of the body portions appear to converge from the top edge ofthe vehicles body towards the underside thereof so as to terminate inmated projections 22 and 23 so as to be nested together in pivotalrelationship.

The front wheel set l3 is rotatably supported on the front portion 11via an axle assembly 25. The rear wheel set 15 is rotatably supported onthe rear body portion 12 via an axle assembly 26, while the centralwheel set 16 is supported by a central axle assembly 27.

Referring to FIGS. 5 and 6, it can be seen that the rear projection 23is extended into a receptacle formed in the front projection 22 so as tobe rotatably nested therein by means of the axle assembly 27. Thecentral axle assembly 27 is sup ported on its opposite ends by bearing28 and by a split axle bearing 30 disposed along the center line of thevehicles body. Power is provided to the central axle from power plant 17via drive sprockets or pulleys 31 and 32 via chains or belts indicatedby numerals 33 and 34 which are suitably coupled to the power planttransmission.

The central axle assembly 27 is composed of a pair of axle segments 35and 36 which are coextensive and are mounted between the split axlebearing 30 and the outside bearing 28, respectively. Such constructionpermits the axle segments to be independently driven by means of thedrive sprockets or pulleys 31 and 32, respectively. It is to beunderstood that the front axle assembly and the rear axle assembly 26are composed of an identical split shaft construction wherein the axleincludes a pair of coextensive segments that are permitted independentand separate rotation. The front right and left axle segments are drivenby means of a pair of drive sprockets or pulleys 37 and 38 carried nearthe end of central axle segments 35 and 36, respectively, and whichinclude a chain or belt drive indicated by numerals 40 and 41 foroperably rotating the axle segments of the front axle assembly 25. Thefront drive sprockets 37 and 38 are enclosed by extensions 42 and 43forming a part of projection 22.

The rear axle assembly segments are independently driven by means ofdrive sprockets or pulleys 44 and 45 via interconnecting chains or belts46 and 47 which form an endless drive about the sprockets or pulleysfixedly mounted on central axle segments 35 and 36 as well as similartypes of sprockets or pulleys mounted on the respective segments of therear axle assembly 26. It is to be noted that rear drive sprockets 44and 45 are housed within the section of projection 23 which is nestedbetween the extensions 42 and 43 of projection 22. Suitable seals andother bearings may be employed to protect the drive sprockets and axleshaft segments from adverse effects of environment whether the vehicleis driven on dusty roads, muddy terrain or through a body of water as anamphibious vehicle. Suitable seals are indicated by numerals 50, 51, 52,and 53 in FIG. 7 which shows the drive train arrangement for rotatingcentral axle segments 35 and 36 for not only rotating wheel set 16 butfor operably driving the wheel axle segments for wheel sets 13 and 15.

In FIG. 8, the drive means for the rear wheel set 15 is illustrated inwhich the central axle segment 35 drives sprocket 44 which in turn isoperably connected to its associated rear axle segment via chain or belt46. Also, the hinge connection between the front projection 22 and therear projection 23 is illustrated so that the front body portion 11 maybe pivotally connected or disposed with respect to the rear body portion12.

Referring now in detail to FIG. 9, an alternate drive means isillustrated wherein each of the wheel sets includes a pair of axlesegments or shafts as previously described. For example, the centralaxle assembly 27 includes coextensive shaft segments 35 and 36, thefront axle assembly 25 includes axle shaft segments 55 and 56 and rearaxle assembly 26 includes shaft segments 57 and 58. Drive sprockets 31and 32 are fixedly secured to the respective shafts 35 and 36 and chainsor belts 33 and 34 operably connect the axle segments to the power planttransmission. However, in place of the drive sprocket and chain or beltand pulley assemblies previously described with respect to powertransmission for driving the front and rear axle assemblies, a pluralityof gear boxes are employed as a substitute. As an example, gear boxes 60and 61 include beveled gears interconnecting the respective axlesegments to intermediate drive shafts 62 and 63 which terminate in abeveled gear arrangement enclosed in rear gear boxes 64 and 65 fordriving the axle segments 57 and 58. The front axle segments 55 and 56are driven by means of gear boxes 66 and 67 housing beveled gears fortransmitting torque to front intermediate drive shafts 68 and 70 havingtheir ends rotatably engaged with front axle segments 55 and 56 viabeveled gears housed within gear boxes 71 and 72. Split axle bearings 73and 74 are employed to rotatably support the opposite ends of the axleassemblies 25 and 26. Bearings 73 and 74 are identical in design andconstruction as bearing 30.

While not illustrated in detail in the drawing, it can be appreciatedthat progressively increasing restraint of the rotational displacementof the body portions may be obtained by incorporating an energyabsorbing means or device 75 between the opposing ends of the bodyportions as indicated in FIG. 4. For example, double-acting, air/oil,shock absorbers could be placed between the body portions opposite faces20 and 21 above the centerline of the central axle. Another means wouldentail the placement of toroidal shaped, rubber springs between thesides of the projections of the body portions. The springs areconcentric with the central axle and have their opposite faces bonded tothe sides of the projections. Another alternative would be toincorporate spiral, torsional springs in the same location as the rubbersprings. In this arrangement, the spindle of the spring is attached toone body portion projection and its end is attached to the other.

The spring on one side of the vehicle would be oriented to progressivelyrestrain upward pitching of the body segments while the spring on theother side would be oriented for action on downward pitching of the bodysegment.

As shown in the drawings, the invention is embodied in a three-axle,six-wheel, all-wheel drive, amphibious vehicle. In this vehicle, a chaindrive or cog belt drive would be used to transmit power from thetransmission to the three axles. The central axle functions as the hingepin to which the projections of the body portions are secured by havingthe axle pass through small holes located in the sides of theprojections. At

the points where the central axle passes through the sides of theprojections, it is mounted in bearings having integral, watertightseals. As may further be determined from the drawing, the central axleis split in half, as are the leading and trailing axles. The inboardends of each half are mounted in a bearing block at the center of thevehicle. The halves of the split axles may be run at differentrotational speeds, or may even be run counterrotationally with respectto each other. The purpose of this arrangement is to make it possible,by the use of a dual output, controllable transmission, to steer thevehicle by imposing differences in the speed of the wheels on the rightand left sides of the vehicle. For example, if the three wheels on theright side of the vehicle are slowed down, stopped, or reversed whilethe wheels on the left side are given more power, the tractive forceproduced on the left side, operating over a lever arm extending acrossthe tread of the vehicle, will cause it to turn to the right, pivotingabout the wheels on the right side. In efiect, a skid-steering system isproduced.

A principal feature of this invention resides in the manner in which thevehicles body portions are hinged to provide for semi-independent,rotational displacement of the body portions in a longitudinal, verticalplane as the portions pivot about a lateral pitch axis.

This hinging action is accomplished by making components of the vehicleperform multiple functions. The central axle mounts the center wheelsand serves as a countershaft for transmission of power to the leadingand trailing axles by means of a chain or belt drive. The central axlealso serves as the hinge pin about which the vehicles body portionspitch in the longitudinal, vertical plane. The body portions, of course,contain the passengers and cargo, provide the space and mounts for thepower package, and carry the axles and wheels. They also function aselements of the hinge. The projection of the rear, or trailing bodyportion, which extends forward across the front, center of the portion,serves as the tenon of the hinge. The two projections extending back oneither side of the front, or leading body portion form between them themortise of the hinge into which the tenon fits. In fabrication of thevehicle, these projections would be integrally formed with the bodyportions.

As is obvious from the foregoing, detailed description of the hinge, avery significant advantage is that it can be easily and readily formedand assembled and requires very few machined, precision parts. Thisminimizes the cost of manufacture, enhances reliability, and simplifiesmaintenance. Also, the manner in which the hinge is configured, whenconsidered in conjunction with the use of a chain drive or cog belt"drive and the utilization of the central axle as a countershaft, greatlysimplifies the transmission of power from one vehicle body portion tothe other and especially when contrasted with the mechanisms employed incontemporary articulated vehicles. Additionally, it facilitates sealingthe body portions for amphibious operation and fully encloses andprotects the drive train from the elements and the entry of dirt andforeign matter.

Two other features of the subject invention are the use of askid-steering system in a multi-element, hinged vehicle, and the factthat the two body portions are prevented from sagging at the hinge pointby virtue of the use of a central axle as the hinge pin.

The overall advantage of hinging the vehicle body portions relates togiving the vehicle the capability to conform to terrain irregularitiesand to maintain maximum ground contact of the wheels in all vehicleattitudes, enhancing traction, braking effect, and vehicle stability.The bending or flexing of the vehicle about the pitch axis also aids inabsorbing the shocks incident to traversing rough, irregular terrain. Itis useful, too, when the vehicle is negotiating a bank coming out ofwater, since it would permit the front, or leading body portion toassume a pitched-up attitude to mount the bank while the rear, ortrailing portion remained level and stable in the water.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader aspects, and, therefore, the aim in theappended claims is to cover all such changes and modifications as fallwithin the true spirit and scope of this invention.

What is claimed is:

l. A pitch-axis articulated vehicle comprising:

a vehicle body having a front body portion and a rear body portion;

hinge means with an axis coincident with the laterally disposed pitchaxis-of said vehicle, said hinge means including a hinge pin connectingthe opposing ends of said front and rear body portions together;

projections included in said hinge means and fixedly carried on andintegrally formed with each of the opposing ends of said front and rearbody portions and arranged in a mated relationship wherein saidprojections carried on a selected body portion include a pair of spacedapart extensions and the other of said projections carried on said otherbody portion is nested between said pair of extenslons;

three wheel sets rotatably supporting said vehicle body on the ground inwhich two of said wheel sets are rotatably carried on said front andrear body portions respectively and said third wheel sets axle isincorporated into said hinge means as the hinge pin and is enclosedwithin and protected by said projections of said front and rear bodyportions; and

power means carried on said vehicle in is operable relationship withsaid wheel sets for imparting a driving force thereto.

2. The invention as defined in claim 1 wherein each of said three wheelsets includes a pair of coextensive axle segments and each of said axlesegments mounts a wheel of its associated one of said wheel sets; andeach of said axle segments is fixedly related to said body portions withrespect to the pointof passage through the sidewalls of said bodyportions and the said integrally formed projections thereof; and

wherein said power means includes a drive train operably connected tosaid axle segments for selectively driving predetermined ones of saidaxle segments to propel and steer the vehicle. 3. The invention asdefined in claim 2 wherein said power means includes a pair of drivemeans directly coupled to said axle segments respectively of said axleassembly associated with said third wheel set; and

intermediate drive means coupling each of said third wheel set axlesegments to said first and second wheel set axle segments associatedwith said front and rear body portions respectively. 4. The invention asdefined in claim 1 wherein each axle assembly includes a pair ofcoextensive axle segments and each of said axle segments mounts a wheelof its associated one of said wheel sets. a

5. The invention as defined in claim 4 wherein said power means includesa drive train operably connected to each of said axle segments forselectively driving predetermined ones of said axle segments. 6. Theinvention as defined in claim 4 wherein said power drive means includesa pair of drive means directly coupled to said axle segmentsrespectively of said axle assembly associated with said third wheel set;and

intermediate drive means coupling each of said third wheel set axlesegments to said first and second wheel set axle segments associatedwith said front and rear body portions respectively.

7. An articulated vehicle comprising:

a vehicle body having a front portion and a rear portion;

a first wheel set including a first axle assembly extending across androtatably carried on said front body portion;

a second wheel set including a second axle assembly extending across androtatably carried on said rear body portion;

a third wheel set disposed between said first and second wheel setsincluding a central axle assembly pivotally coupling said body portionstogether;

separate coupling means operably connected to each of said axles;

power means carried on said vehicle body operably connected to saidcoupling means to independently impart a driving force to each of saidaxles for vehicle movement and steering;

each axle assembly comprising a pair of axle segments having adjacentends rotatably mounted in a split axle bearmg;

said power means being coupledto said central axle segments and saidcentral axle segments being coupled in driving relationship to saidother axle segments;

said front and rear body portions including mated projections pivotallyjoined by said central axle assembly;

said body portions including opposing wall surfaces converging towardssaid projection mounted on said central axle assembly;

said vehicle body portions providing semi-independent rotationaldisplacement in a longitudinal, vertical plane via said central axleassembly about a lateral pitch axis;

said mating projections being each integrally formed with opposing endsof the body portions of which they are a P said semi-independentrotational displacement of the body portions being subjected toprogressively greater constraint by an energy absorbing means disposedbetween the body portions in the area of the pivot;

an energy absorbing means operably coupled between said front and saidrear portions to yieldably restrain pivotal displacement of saidportions relative to each other; and

the opposing wall surfaces of said body portions angularly disposed withrespect to each other in a substantially diverging relationship fromsaid central hinged axis in an upward direction.

I i i

1. A pitch-axis articulated vehicle comprising: a vehicle body having afront body portion and a rear body portion; hinge means with an axiscoincident with the laterally disposed pitch axis of said vehicle, saidhinge means including a hinge pin connecting the opposing ends of saidfront and rear body portions together; projections included in saidhinge means and fixedly carried on and integrally formed with each ofthe opposing ends of said front and rear body portions and arranged in amated relationship wherein said projections carried on a selected bodyportion include a pair of spaced apart extensions and the other of saidprojections carried on said other body portion is nested between saidpair of extensions; three wheel sets rotatably supporting said vehiclebody on the ground in which two of said wheel sets are rotatably carriedon said front and rear body portions respectively and said third wheelset''s axle is incorporated into said hinge means as the hinge pin andis enclosed within and protected by said projections of said front andrear body portions; and power means carried on said vehicle in isoperable relationship with said wheel sets for imparting a driving forcethereto.
 2. The invention as defined in claim 1 wherein eacH of saidthree wheel sets includes a pair of coextensive axle segments and eachof said axle segments mounts a wheel of its associated one of said wheelsets; and each of said axle segments is fixedly related to said bodyportions with respect to the point of passage through the sidewalls ofsaid body portions and the said integrally formed projections thereof;and wherein said power means includes a drive train operably connectedto said axle segments for selectively driving predetermined ones of saidaxle segments to propel and steer the vehicle.
 3. The invention asdefined in claim 2 wherein said power means includes a pair of drivemeans directly coupled to said axle segments respectively of said axleassembly associated with said third wheel set; and intermediate drivemeans coupling each of said third wheel set axle segments to said firstand second wheel set axle segments associated with said front and rearbody portions respectively.
 4. The invention as defined in claim 1wherein each axle assembly includes a pair of coextensive axle segmentsand each of said axle segments mounts a wheel of its associated one ofsaid wheel sets.
 5. The invention as defined in claim 4 wherein saidpower means includes a drive train operably connected to each of saidaxle segments for selectively driving predetermined ones of said axlesegments.
 6. The invention as defined in claim 4 wherein said powerdrive means includes a pair of drive means directly coupled to said axlesegments respectively of said axle assembly associated with said thirdwheel set; and intermediate drive means coupling each of said thirdwheel set axle segments to said first and second wheel set axle segmentsassociated with said front and rear body portions respectively.
 7. Anarticulated vehicle comprising: a vehicle body having a front portionand a rear portion; a first wheel set including a first axle assemblyextending across and rotatably carried on said front body portion; asecond wheel set including a second axle assembly extending across androtatably carried on said rear body portion; a third wheel set disposedbetween said first and second wheel sets including a central axleassembly pivotally coupling said body portions together; separatecoupling means operably connected to each of said axles; power meanscarried on said vehicle body operably connected to said coupling meansto independently impart a driving force to each of said axles forvehicle movement and steering; each axle assembly comprising a pair ofaxle segments having adjacent ends rotatably mounted in a split axlebearing; said power means being coupled to said central axle segmentsand said central axle segments being coupled in driving relationship tosaid other axle segments; said front and rear body portions includingmated projections pivotally joined by said central axle assembly; saidbody portions including opposing wall surfaces converging towards saidprojection mounted on said central axle assembly; said vehicle bodyportions providing semi-independent rotational displacement in alongitudinal, vertical plane via said central axle assembly about alateral pitch axis; said mating projections being each integrally formedwith opposing ends of the body portions of which they are a part; saidsemi-independent rotational displacement of the body portions beingsubjected to progressively greater constraint by an energy absorbingmeans disposed between the body portions in the area of the pivot; anenergy absorbing means operably coupled between said front and said rearportions to yieldably restrain pivotal displacement of said portionsrelative to each other; and the opposing wall surfaces of said bodyportions angularly disposed with respect to each other in asubstantially diverging relationship from said central hinged axis in anupward direction.